Modeling Io's sublimation-driven atmosphere: Gas dynamics and radiation emission

Andrew C. Walker, Sergey L. Gratiy, Deborah Levin Fliflet, David B. Goldstein, Philip L. Varghese, Laurence M. Trafton, Chris H. Moore, Benedicte Stewart

Research output: Contribution to journalConference articlepeer-review


Io's sublimation-driven atmosphere is modeled using the direct simulation Monte Carlo method. These rarefied gas dynamics simulations improve upon earlier models by using a three-dimensional domain encompassing the entire planet computed in parallel. The effects of plasma impact heating, planetary rotation, and inhomogeneous surface frost are investigated. Circumplanetary flow is predicted to develop from the warm subsolar region toward the colder night-side. The non-equilibrium thermal structure of the atmosphere, including vibrational and rotational temperatures, is also presented. Io's rotation leads to an asymmetric surface temperature distribution which is found to strengthen circumplanetary flow near the dusk terminator. Plasma heating is found to significantly inflate the atmosphere on both day- and night-sides. The plasma energy flux also causes high temperatures at high altitudes but permits relatively cooler temperatures at low altitudes near the dense subsolar point due to plasma energy depletion. To validate the atmospheric model, a radiative transfer model was developed utilizing the backward Monte Carlo method. The model allows the calculation of the atmospheric radiation from emitting/absorbing and scattering gas using an arbitrary scattering law and an arbitrary surface reflectivity. The model calculates the spectra in the v 2 vibrational band of SO 2 which are then compared to the observational data.

Original languageEnglish (US)
Pages (from-to)1085-1090
Number of pages6
JournalAIP Conference Proceedings
StatePublished - Apr 13 2009
Externally publishedYes
Event26th International Symposium on Rarefied Gas Dynamics, RGD26 - Kyoto, Japan
Duration: Jul 20 2008Jul 25 2008


  • Atmosphere
  • Io

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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